This invention relates to a device for limiting the number of revolutions of a shaft of a rotary drive for a sliding roof of an automobile.
A device of type is known from DE 23 33 666 C3, which comprises an eccentric disc secured to the shaft and having an externally toothed ring rotatably journalled upon its circumferential surface, the ring being surrounded by an internal set of teeth fixed in a rose and concentrically to the shaft axis, the tooth root radius (dedendum radius) of which external teeth is greater than the tooth crest radius (addendum radius) of the toothed ring approximately by the amount of the eccentricity of the eccentric disc, wherein abutment means for the limiting position of the shaft after predetermined numbers of revolutions have been reached are connected on the one hand to the toothed ring and on the other hand to the rose, wherein the abutment means connected to the rose is a blocking pin slidably guided parallel to the shaft, the pin being capable of engaging into or disengaging from the path of the abutment means connected to the toothed ring only in one specific setting of the toothed ring, whereby said pin permits both directions of rotation when engaged and, in its disengaged position, the drive is blocked in both directions of rotation, and wherein the abutment means connected to the toothed ring are formed as peripheral steps of a blocking ring, which is journalled rotatably and concentrically to the shaft in the rose and is provided with a radial groove into which an entraining pin fixed to the toothed ring engages, and the blocking ring being furnished between the peripheral steps with an annular shoulder which is interrupted at a fixed position, corresponding to the zero setting, to permit passage of the blocking pin, and the blocking pin, provided with a rotation preventer, possesses a transverse recess for engagement with the annular shoulder.
With this proven device, it is possible, for two different movement sequences that can be carried out by the same shaft, namely optionally sliding or pivoting out/pivoting in of the sliding lid in sliding-lifting roofs, in spite of the different setting displacements for these two movement sequences to be limited by means of this device, to provide only one indexing position, with the result that operation of the sliding roof equipped with two setting functions is considerably simplified.
With this known device, starting from the zero setting in which the blocking pin alone can be actuated, at the commencement of one of the two movement sequences, or in transition from one movement sequence to the other, for example the transition from the sliding movement after the roof has been closed into the outward pivotal movement, the blocking pin simply needs to be engaged into the path of the abutment means connected with the toothed ring in order to cancel out the rotation blocking. The blocking ring here fulfils two functions, namely on the one hand it carries the displacement-limiting abutment means and on the other hand it firmly holds with its annular shoulder the engaged blocking pin, so that the drive can be actuated in both directions of rotation. A disengagement of the blocking pin for blocking the rotational movements is possible here at only one single position, i.e. when the lid closed position has been reached. Along the entire travel of the lid closure and outward pivotal movement, the blocking pin remains engaged, so that it is not possible to block the drive and thereby the lid movement by disengaging the blocking pin in an intermediate position, for example during the opening sliding of the lid, just before the maximum opened position is reached, or during the outward pivotal movement when the lid is only half-opened. Frequently, however, it is desired to reach a specific lid setting without the need to check the opening operation by visual inspection, for example in order to maintain an accustomed roof opening, or in order to prevent air vibrations occurring at specific speeds of travel. Also, when the blocking pin is engaged and thus the rose is not blocked, the sliding lid is not secured against sudden sliding closure, for example due to inertia forces resulting from jerky stopping of the vehicle, when the lid has been slid into an intermediate position or into the maximum opened setting. Where the lid is pivoted out only partly into a ventilating position, this lid, when the blocking pin is engaged end thus the rose is not blocked, is not effectively secured against unauthorized movement of the rear edge of the lid from outside.